1. Field of the Invention
The present invention relates to a processing apparatus and method for automatically performing processes such as polishing on workpieces made of ceramics or the like to form them into desired dimensions.
2. Description of the Related Art
Processing apparatuses for processing workpieces made of ceramics or the like include polishing apparatuses such as grinding, lapping and polishing apparatuses. Some of such processing apparatuses including polishing apparatuses have an automatic sizing function for automatically controlling a processing operation to form a workpiece into desired dimensions. For example, there are four types of conventional processing apparatuses having the automatic sizing function as described below.
A processing apparatus of a first type acquires a certain signal from a workpiece (e.g., the resistance of a resistor embedded in the workpiece) and recognizes the present state (thickness, the distance to a target position, etc.) of the workpiece based on the signal to control a processing operation.
A processing apparatus of a second type controls a processing operation based on only a signal from a machine control system (e.g., information on the directions of three orthogonal spindles and the rotating direction).
A processing apparatus of a third type controls a process by setting a processing time based on processing conditions, and the method of control depends on the judgement of the operator or know-how.
A processing apparatus of a fourth type recognizes a process starting position and controls a processing operation based on displacement from the same position.
Steps for a polishing process operation utilizing a processing apparatus of the third type will now be described with reference to the flow chart in FIG. 9 as an example of steps for a polishing process operation utilizing a polishing apparatus according to the related art. In the process operation, the dimensions of a workpiece is first measured, and a processing time is set in the processing apparatus according to the same (step S201). At this time, the processing time is set such that the dimensions of the workpiece become predetermined dimensions larger than desired dimensions in order to prevent the workpiece from being over-polished. Next, the workpiece is secured to a keeper for holding the workpiece (step S202). The keeper is then secured to the processing apparatus (step S203). Next, the workpiece is processed (step S204). The processing apparatus then determines whether the processing time has reached the set tome or not (step S205). If not (N), the process at step S204 is continued. If the processing time has reached the set time (step S205; Y), the process is stopped, and the dimensions of the workpiece are measured and evaluated (step S206). Next, it is determined whether the evaluation has been passed or not (step S207). If not (N), a processing time is newly set (step S208), and the process returns to step S204 to perform further processing. If the evaluation has been passed (step S207; Y), the process operation is terminated.
A processing apparatus of the first type has a problem in that it inevitably involves a pre-process to allow the acquisition of a signal from a workpiece. Further, some products cannot be processed using a processing apparatus of the first type.
A processing apparatus of the second or fourth type has a problem in that it becomes more costly as processing accuracy is improved because the accuracy of the machine control system (rigidity against a slide, temperature characteristics, etc.) must be improved in order to improve processing accuracy. A processing apparatus of the second or fourth type cannot be used as a processing apparatus such as a chemimechanical polishing (CMP) apparatus in which an elastic body such as a polishing cloth (pad) is interposed between a workpiece and a surface plate. In the case of a processing apparatus of the fourth type, it is essential to provide a step of comparing the data of the current processing position and the data of the process starting position in order to detect displacement from the process starting position, which results in a problem in that the number of processing steps is increased.
A processing apparatus of the third type has a problem in that the processing accuracy is low because it has significant variation of processing depending on the state of the surface plate, slurry and the like and the operator. Further, it has a problem in that a workpiece must be measured before and after processing without fail and in that it has low operating efficiency because the processing step (step S204) and measurement/evaluation step (S206) must normally be repeated two or more times as apparent from FIG. 9.
It is an object of the invention to provide a processing apparatus and method for automatically processing a workpiece into desired dimensions which make it possible to improve processing accuracy and efficiency without any need for a special pre-process.
A processing apparatus according to the invention comprises:
a processing machine which performs a predetermined process on a workpiece;
a first detector which detects a reference position;
a second detector which detects a position associated with a dimension of the workpiece which changes as a result of the process; and
a controller which recognizes the dimension of the workpiece based on the reference position detected by the first detector and the position detected by the second detector and controls the processing machine such that the dimension of the workpiece becomes a predetermined value.
In the processing apparatus according to the invention, the first detector detects the reference position; the second detector detects the position associated with the dimension of the workpiece which changes as a result of the process; and the controller recognizes the dimension of the workpiece based on the positions detected by the two detectors and controls the processing machine such that the dimension of the workpiece becomes the predetermined value.
The processing machine of the processing apparatus according to the invention may polish the workpiece.
The first detector and second detector of the processing apparatus according to the invention may be mounted on the same arm.
The first detector and second detector of the processing apparatus according to the invention may intermittently perform the detecting operation.
The controller of the processing apparatus according to the invention may recognize the dimension of the workpiece based on the result of detection performed plural times by the first detector and the second detector.
A processing method according to the invention is a method for processing a workpiece utilizing a processing apparatus having a processing machine which performs a predetermined process on the workpiece, a first detector which detects a reference position and a second detector which detects a position associated with a dimension of the workpiece which changes as a result of the process, the method comprising the steps of:
detecting the reference position with the first detector and detecting the position associated with the dimension of the workpiece which changes as a result of the process with the second detector;
recognizing the dimension of the workpiece based on the reference position detected by the first detector and the position detected by the second detector; and
performing the process by controlling the processing machine based on the recognized dimension such that the dimension of the workpiece becomes a predetermined value.
In the processing method according to the invention, the processing machine may polish the workpiece.
In the processing method according to the invention, the first detector and second detector may be mounted on the same arm.
In the processing method according to the invention, the detecting step may intermittently detect the positions.
In the processing method according to the invention, the recognizing step may recognize the dimension of the workpiece based on the result of detection performed plural times by the first detector and the second detector.
Other objects, features and advantages of the invention will become sufficiently apparent from the following description.